The present invention relates to a cylindrical guide rail for guiding nondestructive flaw detector and more particularly to a clamping device for securing the cylindrical guide rail aroung a cylindrical object to be inspected such as a pipe.
In the case of nuclear power plant, various regulations are provided which require periodical inspections of pipes or nozzles by using a nondestructive detector such as an ultrasonic flaw detector. Generally, those inspections are accomplished by manipulating the detector around the object to be inspected from a remote location to prevent operators from radiation damage. The detector is manipulated circumferencially and axially around the pipe by remote control along a cylindrical guide rail which is secured around the surface of the object. In order to perform inspections accurately, the guide rail must be clamped to the object securely. Also, the guide rail must be mounted and dismounted in as short time as possible to minimize the radiation damage of the operator, because mounting and dismounting operations can not be performed by remote control. Further, the guide rail must be adjustable for various size of pipes, because there are so many pipes in the plant, which have various size in diameter.
Various clamp mechanisms have been proposed to secure the guide rail around the pipe, for example, in the U.S. Pat. No. 3,921,440, an inflatable bladder is arranged between inner surfaces of the guide rail and outer periferal surfaces of the pipe. However, this type of bladder is not duarable for a pipe of high temperature. Another known clamping mechanism is to provide a plurality of clamp screws around the guide rail, which are adjustably extending in the radial direction toward the pipe. However, as each clamp screw must be adjusted independently, it is difficult to secure the guide rail coaxially about the cylindrical pipe. Also, it takes long to mount or dismount the guide rail as there are so many clamp screws necessary.
It is therefore an object of the present invention to provide an improved cylindrical guide rail which can be mounted and dismounted for a shorter operating period with simple and duarable mechanisms.
According to a preferred embodiment of the present invention, a split cylindrical ring which has a plurality of adjustable jacks circumferencially around the inner peripheral surface of the ring is obtained. Each jack adjustably moves respective clamp shoes provided on the jack in the radial direction of the ring so as to clamp a circular object to be inspected. Each jack is connected by a single force transmitting means through which the adjustment of respective clamp shoes is attained.
Because of a simple clamp mechanism, the weight of the guide rail has advantageously reduced. Further, as each jack is connected by the force transmitting means and the adjustment of the respective clamp shoes can be made by a single operation of the force transmitting means, the clamp operation is advantageously shortened and the adjustment of the guide rail in the axis of the object has remarkably made easier.
Also, by the use of jacks for the clamp mechanism, clamp force required has remarkably reduced and no special tool for the clamp operation is necessary.
The clamp mechanism of the present invention is especially preferred in case where the diameter of the object to be inspected varies in a large extent.
Further objects and advantages of the present invention will be explained with reference to the following drawings.